15 Jan Field observations on heat sterilizing an infested stuffed chair
There have been a few lab experiments on how bed bugs react to heat. The experiments suggested the bugs would generally not venture far from the harbourage but would actually come out of the harbourage with foraging behaviour and when it became too hot they would return to the harbourage. This was good news for the whole home heat sterilizers as the natural implication was the bugs might not run to surrounding cooler areas or suites.
In the hundreds of heat loads I have performed I rarely notice the dead bugs remaining in the harbourages. In fact the bugs come out of their harbourages and I find them dead on the floor of the trailer. These bugs never returned to the harbourage. I am not sure if the above experiment found the bugs dead in the harbourage or near the harbourage but in my experience I have found the bugs do not die in the harbourage.
I was asked to heat sterilize a stuffed arm chair with a removable cushion. When we arrived we inspected the chair, which included removing the cushion, and no bed bugs were found directly under the cushion. In fact, in the 1000 plus suites I have treated for bed bugs I have never seen a bug under the cushions of a couch or chair – the bugs are rather hidden in cracks and crevices. We then replaced the cushion and carried the chair to the heat trailer. I returned the trailer to my shop and plugged in the equipment. But, because I was preoccupied with another appointment, I neglected to remove the cushion from the chair to facilitate maximum heat penetration. About 2 hours into the treatment, with average trailer temperatures in the 140f range I realized that I had forgotten to remove the cushion. I entered the trailer and removed the cushion. Amazingly I found about a dozen bugs milling about in an agitated fashion directly under the cushion in what would have been the coolest spot in the chair.
This small accidental experiment suggests that bed bug behaviour is not as simple as the earlier experiment suggested. I suspect the author of the earlier study was not incorrect in his observations but rather bed bugs have a range of potential behaviours when subjected to different circumstances. The stuffed chair case suggests, at minimum, some of the bugs actively sought the coolest spot on the chair when subjected to lethal temperatures. Whole home heat treaters would not find this study appealing as it demonstrates that there are situations where bugs actively seek cooler harbourage when subjected to heat. Once again we see that bed bug behaviour is complex. Bed bugs, when subjected to different situations, and indeed even different bugs, exhibit a range of behaviours.